My former prospective father-in-law was a civil engineer in southeastern Virginia (Virginia Beach). Beautiful area, but all the large buildings sit on piles driven about 300 feet in the ground. I suspect that Gaza would recover, regardless, but hunkering down in tunnels like those is militarily suicidal. All it does is spare you from the immediate effects of artillery and airstrikes. Eventually you have to come up and defend the entrances and ventilation system or die.
Whoever in Hamas decided that such an extensive tunnel system was a good idea wasted a lot of money and man hours. Tunnels are great for building up stores but aren’t squat for hiding out in, especially if your enemy uses artillery and air power to take out your above ground weapons and fighters.
I imagine there are a bunch of Hamas cadre stuck in those tunnels scratching their heads and wondering “what now.”
Unless they used the cease fire to get a bunch of them out.